In the field of magnetic domain devices, materials that exhibit magnetic domain characteristics, the behavior of such magnetic domains, and the use of these magnetic domain materials in sensing and display devices have been described: see United Kingdom Pat. No. 1,180,334; Krumme, J-P. et al., "Ferrimagnetic Garnet Films of Magneto-optic Information Storage", IEEE Transactions on Magnetics, Vol. Mag-11, No. 5, September 1975, page 1097; Lacklison, D. E. et al., "The Magneto-optic Bubble Display", IEEE Transactions on Magnetics, Vol. Mag-13, No. 3, May 1977, page 973; Lacklison, D. E. et al., "Magnetic-Optic Displays", IEEE Transactions on Magnetics, Vol. Mag-13, No. 3, May 1977, page 973; Lacklison, D. E. et al., "Magneto-Optic Displays", IEEE Transactions on Magnetics, Vol. Mag-11, No. 5, September 1975, page 1118; Hill, B. and Schmidt, K. P., "Fast Switchable Magneto-Optic Memory Display Components", Philips Journal of Research, Volume 33, Nos. 5/6, 1978, page 211; Almasi, G. S., "Magneto-optic Bubble-Domain Devices", IEEE Transactions on Magnetics, Vol. Mag-7, No. 3, September 1971, page 370; U.S. Pat. No. 3,815,107; and, U.S. Pat. No. 3,526,883.
Magneto-optic or magnetic domain display devices can employ either the Faraday effect which depends on the change in rotation of the plane of polarization of electromagnetic radiation, such as polarized light, as it is transmitted through a magnetic domain, or the Kerr effect which depends on radiation reflected by a magnetic domain. In accordance with the Faraday effect, if the transmitted radiation is plane polarized, passed through a magnetic domain, and then through an analyzer, the intensity of the radiation which has been so transmitted is either greater than or less than that radiation which is transmitted through adjoining domains, as opposite direction of magnetization provided that the analyzer is adjusted to extinguish radiation in one direction of magnetization. This resulting contrast in radiation intensities is the basis for magnetic domain display devices.
One form of magnetic domain display devices utilize the propagation of magnetic domains either along a propagation track (U.S. Pat. Nos. 3,526,883; 3,815,107 and 3,824,570), or inhibit the migration of a propagated magnetic domain by positioning a ferrimagnetic material on the magnetic domain material (U.S. Pat. Nos. 3,516,883 and 3,893,023), or etch or scribe a line in the material surface (U.S. Pat. No. 3,798,622).
Propagation of magnetic domains can also be controlled by guide channels or mesas (MAGNETIC BUBBLES, Selected Topics in Solid State Physics-Volume XIV by A. H. Bobeck and E. Della Torre, North-Holland Publishing Company, Amsterdam, Holland, 1975, pp 165-5), and by stable magnetic domain positions having channel walls which act as high energy barriers (U.S. Pat. No. 4,059,829).
Since the propagation of magnetic domains is not always desired, another form of magnetic domain display devices utilize an individual and intrinsic magnetic domain that is physically constrained so that the domain generally cannot move, while the direction of magnetization of the individual and intrinsic magnetic domain can be changed or switched ("Fast Switchable Magneto-Optic Memory Display Components", supra; and U.S. Pat. No. 4,114,191).
When it is necessary to change the direction of magnetic orientation of a magnetic domain, and the domain is a single wall region closed upon itself, the field required to annihilate or change a selected magnetic domain is relatively high so that an external bias field is required (U.S. Pat. No. 4,114,191). Where an external bias field is not required, the physical orientation of the drive lines with respect to a memory area or defined volume becomes complex and, therefore, costly (United Kingdom Pat. No. 1,180,334).
This invention, a magnetic domain device for the control of electromagnetic radiation, overcomes the disadvantages of the prior art by drive lines configured to complement the physical geometry of a volume of a material that exhibits magnetic domain characteristics. This also results in a significant reduction in the drive field required to change the direction of magnetic orientation of a region in the volume that is partly defined by a single wall which is not closed upon itself as is a conventional magnetic bubble domain, and eliminates the need for an external bias field.